One of the many pleasures of summer is cool refreshing watermelon. According to scientists from the U.S. Department of Agriculture, the temperature of your watermelon determines how nutritious it is. Icy-cold watermelon carries the least nutrients, while room temperature melon is even more nutritious than those just picked off the vine.

Watermelon is rich in carotenoids, antioxidants that prevent damage caused by the sun and exposure to environmental chemicals. Lycopene is one such antioxidant, which specifically prevents heart disease. It also makes watermelon and tomatoes the color red. Watermelon continues to produce nutrients such as lycopene and beta-carotene even after they are picked -- as long as they are not stored too cool for too long, which slows the ripening process. The study showed that watermelons stored at 70 degrees Fahrenheit increased 40 percent in lycopene and 50 to 139 percent in beta-carotene.

Sudden cardiac death rates climb as winter temperatures drop -- and the freezing cold is responsible, according to a new study. Cold stress on the circulatory system causes blood pressure to rise, thickening and clotting of the blood, and strain on the heart.

The 24-year study was conducted in Olmstead County, Minnesota, a region that endures a wide-range of temperatures throughout the year, including severe winter cold. Researchers studied the relationship of cardiac incidence to season, daily temperature, and moisture. Sudden cardiac death, occurring when the heart stops beating suddenly, rose 17 percent more in the winter than in the summer. When temperatures dropped below 32 degrees Fahrenheit (0 Celsius), the risk jumped another 20 percent. However, the risk of heart attack, or artery blockage preventing blood from flowing into the heart, did not increase.

Interestingly, most of the sudden cardiac fatalities in the study did not have a history of heart disease. Researchers speculate that these folks spent more time outdoors in the extreme temperatures, not having been advised to stay out of the cold as a heart patient would.

Record-high temperatures propelled European government agencies to protect its citizens this week. In 2003, a disastrous heat wave killed 15,000 French and 2,000 British people -- affecting many seniors, especially those who live alone. Many of these deaths could be attributed to the rise in heart risk as temperatures climb.

This year, an 85-year-old man taken to a hospital and an 81-year-old woman found in her home were the first of nine to have died from the heat in France. With temperatures higher than ever, government officials across the Union have come to realize the need for extra specialized attention necessary for the elderly during heat waves. As a preventative strategy, Britain began paying extra visits to this vulnerable segment of the population.

Steady high temperatures and humidity have an adverse effect on the cardiovascular system, often resulting in higher risk of heart attacks in the elderly. Researchers studying heart attack rates in Athens, Greece, found an increase of mortality in people over age 70-- linked directly to a consistent rise in temperature and humidity. The heat in 2001 may have been responsible for 3,126 deaths caused by heart attack. The body suffers much stress in high temperatures, which takes its toll on the circulatory system.

Death from heart attack is also high in the month of December, according to the researchers. The affect, known as the Merry Christmas Syndrome, is a result of the combination of holiday over-indulgences in food and alcohol combined with emotional stress.